Clock



FIG. 1 shows a perspective view for my design for a clock;

FIG. 2 shows a front view thereof;

FIG. 3 shows a rear view thereof;

FIG. 4 shows a left side view thereof;

FIG. 5 shows a right side view thereof;

FIG. 6 shows a top view thereof; and,

FIG. 7 shows a bottom view thereof.

The broken line showings are for illustrative purposes only and form no part of the claimed design. 

The ornamental design for a clock, as shown and described. 